The present invention generally relates to techniques for transmitting images between computers using encoded image files and in particular, to a method and apparatus for transmitting image updates employing high compression encoding.
There are a number of well-known graphics formats that allow easy storage and transmission of image files between computers. To minimize the size of the files and the time it takes to download them, some of these graphics formats employ data compression.
When transmitting a sequence of images, each image in the sequence may only be modestly different than an immediately prior image. Therefore, to further reduce the size of the image files and the time it takes to download them it is desirable to store and transmit only update portions of the images. Unfortunately, when information for the full screen or a full rectangular window of the screen must be transmitted each time, unchanged as well as changed portions of the images must be transmitted, thus preventing realization of the full savings from such an approach.
Accordingly, it is an object of the present invention to provide a method for transmitting image file updates employing high compression encoding.
Another object is to provide an apparatus for transmitting image file updates employing high compression encoding.
These and additional objects are accomplished by the various aspects of the present invention, wherein briefly stated, one aspect is a method for transmitting image updates employing high compression encoding, comprising: comparing new image pixel values against old image pixel values at corresponding coordinates respectively of a new image and an old image; providing new image pixel values for coordinates where the new image pixel values are significantly different than the old image pixel values and not equal to a transparent pixel value; and providing the transparent pixel value for coordinates where the new image pixel values are not significantly different than the old image pixel values.
In another aspect, an apparatus for transmitting image updates employing high compression encoding comprises circuitry for comparing new image pixel values against old image pixel values at corresponding coordinates respectively of a new image and an old image; providing new image pixel values for coordinates where the new image pixel values are significantly different than the old image pixel values and not equal to a transparent pixel value; and providing the transparent pixel value for coordinates where the new image pixel values are not significantly different than the old image pixel values.
In still another aspect, an apparatus for transmitting image updates employing high compression encoding comprises means for comparing new image pixel values against old image pixel values at corresponding coordinates respectively of a new image and an old image; means for providing new image pixel values for coordinates where the new image pixel values are significantly different than the old image pixel values and not equal to a transparent pixel value; and means for providing the transparent pixel value for coordinates where the new image pixel values are not significantly different than the old image pixel values.
Additional objects, features and advantages of the various aspects of the present invention will become apparent from the following description of its preferred embodiment, which description should be taken in conjunction with the accompanying drawings.